DEVELOPMENT OF SHEAR WAVE VELOCITY EXPLORATION SYSTEM BASED ON MICROTREMOR MEASUREMENTS AND IT'S APPLICATION TO SITE CHARACTERISTCS

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The objects of this study is to develop a technique for estimating shear wave velocity structures using both the dispersion characteristics and the H/V spectra that can readily be obtained from microtremor measurements and to examine it's application for the evaluation of dynamic response characteristics of a site. For this purpose, (1), analytical formulas are presented for computing the H/V ratios of microtremors, assuming, that microtremors consist of Rayleigh and surface waves, (2) an inverse analysis using H/V spectra is developed for estimating a shear wave velocity structure under appropriate constraint conditions, (3) a theory and a field technique as well as observation system are introduced for estimating two-dimensional shear wave velocity structure using both microtremor dispersion curve and H/V spectra, (4) the effectiveness of the proposed method is examined based on microtremor measurements at sites for which shear, wave velocity structure is available, and (5) dynamic r … More esponse analyses are conducted using the two-dimensional shear wave velocity structures that are estimated from the proposed method for the regions where either strong motion array records or spatial variation of damage was obtained during the Kushiro-oki and Hyogoken-Nambu earthquakes.It is shown that:(1) The H/V ratios of surface waves are in fairly good agreement with those of microtremors;(2) VィイD2sィエD2 profiles of subsurface soils may be estimated from the H/V ratios of microtremors using the proposed formulas,.(3) The microtremor measurements in Kushiro and Kobe confirm the effectiveness of the proposed method for outlining three-dimensional soil profiles with varying thickness of surface layer overlying bedrock, and(4) The computed spatial variation in acceleration from two-dimensional shear wave velocity structures estimated from microtremors are consistent with those observed in the field, indicating that the effectiveness of an economical means of estimating two- or three-dimensional shear structure Less